enumerate 枚舉

enumerate(iterable, start=0)

Return an enumerate object. iterable must be a sequence, an iterator, or some other object which supports iteration. The __next__()method of the iterator returned by enumerate() returns a tuple containing a count (from start which defaults to 0) and the values obtained from iterating over iterable

將一個可支持叠代的對象，轉化為枚舉， 所以列表，序列，或者其他可叠代的對象即可以；枚舉會返回一個包含數字和叠代器中的值的元組；最終返回一個可枚舉對象；

典型用法：

seasons = [‘Spring‘, ‘Summer‘, ‘Fall‘, ‘Winter‘]

list(enumerate(seasons))

[(0, ‘Spring‘), (1, ‘Summer‘), (2, ‘Fall‘), (3, ‘Winter‘)]

簡單實現：

def enumerate(sequence, start=0):
    n = start
    for x in sequence:
        yield n, x
        n += 1

Python標準庫-enumerate用法